South African union says 36,000 mining jobs under threat in next 3 months

* South Africa mining sector hit by weak metal prices

* NUM membership falls below 200,000, lowest in three decades (Adds details)

JOHANNESBURG, Feb 29 (Reuters) - South Africa's National Union of Mineworkers (NUM) said on Monday more than 36,000 jobs could be lost in the embattled industry over the next three months, around 7 percent of the roughly 500,000-strong labour force.

The South African mining industry is under pressure from sinking metal prices and soaring costs which have triggered a fresh wave of layoffs across a sector that has shed hundreds of thousands of jobs over the past two decades.

The jobs immediately under threat have been announced by several companies including Anglo American (LSE: AAL.L - news) units Kumba Iron Ore and Anglo American Platinum.

The NUM General Secretary David Sipunzi told a media briefing that the union hoped talks with the companies - part of the legal process before workers can be laid off - would result in fewer jobs being lost.

Sipunzi also said that job cuts had seen the union's membership numbers fall from 206,000 in 2015 to 198,000 in January - the first time the union's numbers have fallen below 200,000 since its formation in the 1980s.

The union has also lost tens of thousands of members to arch-rival the Association of Mineworkers and Construction Union (AMCU) in a bloody turf war in South Africa's platinum belt.

The NUM's falling membership will also be a concern for the ruling African National Congress (ANC) because the union, among others, is a key political ally of the party, which faces a tough test from opposition parties in local elections this year. (Reporting by Ed Stoddard; Editing by James Macharia)